The Zend Framework By Examples site has posted a recent tutorial about using the Zend_Date component of the Zend Framework to work with dates and times in your PHP applications.
In this example, we get or set dates in different timezones. We display parts of dates and times in various formats. We also get information on sunrise and sunset in several locations.
They also incorporate other components in the examples including Zend_Cache, Zend_Locate and Zend_Registry. Their examples show how to check the locale, verify the timezone and figure out a "date from now". Complete code is included - it's not the best method to handle some parts of the example, but it's a rough guide in the right direction.